Perchlorate and chlorate assessment in drinking water in northern Chilean cities.

Perchlorate and chlorate are endocrine disruptors considered emerging contaminants (ECs). Both oxyanions are commonly associated with anthropogenic contamination from fertilizers, pesticides, explosives, and disinfection byproducts. However, the soils of the Atacama Desert are the most extensive natural reservoirs of perchlorate in the world, compromising drinking water sources in northern Chile. Field campaigns were carried (2014-2018) to assess the presence of these ECs in the water supply networks of twelve Chilean cities. Additionally, the occurrence of perchlorate, chlorate and other anions typically observed in drinking water matrices of the Atacama Desert (i.e., nitrate, chloride, sulfate) was evaluated using a Spearman correlation analysis to determine predictors for perchlorate and chlorate. High concentrations of perchlorate (up to 114.48 µg L-1) and chlorate (up to 9650 µg L-1) were found in three northern cities. Spatial heterogeneities were observed in the physicochemical properties and anion concentrations of the water supply network. Spearman correlation analysis indicated that nitrate, chloride, and sulfate were not useful predictors for the presence of perchlorate and chlorate in drinking water in Chile. Hence, this study highlights the need to establish systematic monitoring, regulation, and treatment for these EC of drinking water sources in northern Chilean cities for public health protection.

Challenges and opportunities for drinking water treatment residuals (DWTRs) in metal-rich areas: an integrated approach.

The physicochemistry and production rate of drinking water treatment residuals (DWTRs) depends on the raw water composition and the plant operational parameters. DWTRs usually contain Fe and/or Al oxyhydroxides, sand, clay, organic matter, and other compounds such as metal(oids), which are relevant in mining countries. This work proposes a simple approach to identify DWTRs reuse opportunities and threats, relevant for public policies in countries with diverse geochemical conditions. Raw water pollution indexes and compositions of DWTRs were estimated for Chile as a model case. About 23% of the raw drinking water sources had moderate or seriously contamination from high turbidity and metal(loid) pollution If the untapped reactivity of clean DWRTs was used to treat resources water in the same water company, the 73 and 64% of these companies would be able to treat water sources with As and Cu above the drinking water regulations, respectively. Integrating plant operational data and the hydrochemical characteristics of raw waters allows the prediction of DWTRs production, chemical composition, and reactivity, which is necessary to identify challenges and opportunities for DWTRs management.

An integrated study of health, environmental and socioeconomic indicators in a mining-impacted community exposed to metal enrichment.

The occurrence of toxic metals and metalloids associated with mine tailings is a serious public health concern for communities living in mining areas. This work explores the relationship between metal occurrence (e.g., spatial distribution in street dusts), human health indicators (e.g., metals in urine samples, lifestyle and self-reported diseases) and socioeconomic status (SES) using Chañaral city (in northern Chile) as study site, where a copper mine tailing was disposed in the periurban area. This study model may shed light on the development of environmental and health surveillance plans on arid cities where legacy mining is a sustainability challenge. High concentrations of metals were found in street dust, with arsenic and copper concentrations of 24 ± 13 and 607 ± 911 mg/kg, respectively. The arsenic concentration in street dust correlated with distance to the mine tailing (r = - 0.32, p-value = 0.009), suggesting that arsenic is dispersed from this source toward the city. Despite these high environmental concentrations, urinary levels of metals were low, while 90% of the population had concentrations of inorganic arsenic and its metabolites in urine below 33.2 µg/L, copper was detected in few urine samples (< 6%). Our results detected statistically significant differences in environmental exposures across SES, but, surprisingly, there was no significant correlation between urinary levels of metals and SES. Despite this, future assessment and control strategies in follow-up research or surveillance programs should consider environmental and urinary concentrations and SES as indicators of environmental exposure to metals in mining communities.

Active and legacy mining in an arid urban environment: challenges and perspectives for Copiapó, Northern Chile.

Urban expansion in areas of active and legacy mining imposes a sustainability challenge, especially in arid environments where cities compete for resources with agriculture and industry. The city of Copiapó, with 150,000 inhabitants in the Atacama Desert, reflects this challenge. More than 30 abandoned tailings from legacy mining are scattered throughout its urban and peri-urban area, which include an active copper smelter. Despite the public concern generated by the mining-related pollution, no geochemical information is currently available for Copiapó, particularly for metal concentration in environmental solid phases. A geochemical screening of soils (n = 42), street dusts (n = 71) and tailings (n = 68) was conducted in November 2014 and April 2015. Organic matter, pH and elemental composition measurements were taken. Notably, copper in soils (60-2120 mg/kg) and street dusts (110-10,200 mg/kg) consistently exceeded international guidelines for residential and industrial use, while a lower proportion of samples exceeded international guidelines for arsenic, zinc and lead. Metal enrichment occurred in residential, industrial and agricultural areas near tailings and the copper smelter. This first screening of metal contamination sets the basis for future risk assessments toward defining knowledge-based policies and urban planning. Challenges include developing: (1) adequate intervention guideline values; (2) appropriate geochemical background levels for key metals; (3) urban planning that considers contaminated areas; (4) cost-effective control strategies for abandoned tailings in water-scarce areas; and (5) scenarios and technologies for tailings reprocessing. Assessing urban geochemical risks is a critical endeavor for areas where extreme events triggered by climate change are likely, as the mud flooding that impacted Copiapó in late March 2015.